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Novel components of Acacia mearnsii

- Ilsley, Anthony Hugh

Authors: Ilsley, Anthony Hugh
Date: 1969
Language: English
Type: Thesis , Masters , MSc
Identifier: vital:21164 , http://hdl.handle.net/10962/6673
Description: From Summary: From the complex mixture of flavonoid components present in the heartwood of the black wattle tree (Acacia mearnsii) four new compounds have been isolated. These include a novel dioxane-linked dimeric proanthocyanidin based on leucofisetinidin. This is the first proanthocyanidin of its type to be isolated from a natural source. I solation was achieved by standard counter current partition separation and preparative paper chromatographic techniques. The compound, which forms an anthocyanidin, was identified by micro-degradation, and n.m.r. and mass spectrometry. Comparison of the spin-spin coupling constants of the heterocylic rings' protons with those of authentic monomeric flavan-3, 4-diols showed that the heterocyclic rings of the two symmetrical flavan moeities have 2,3-trans-3,4-cis configurations. Dreiding models suggest that the central dioxane ring has a half-boat conformation while the heterocyclic rings of the two flavan units have five point coplanar conformations. Two possible absolute configurations have been proposed
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Date Issued: 1969

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Ray tracing at very low frequencies when the effects of heavy ions are considered

- Terry, Patrick D.

Authors: Terry, Patrick D.
Date: 1969
Subjects: Ionospheric radio wave propagation , Ionosphere -- Graphic methods , Ray tracing algorithms
Language: English
Type: Thesis , Masters , MSc
Identifier: vital:5542 , http://hdl.handle.net/10962/d1013350
Description: The behaviour of very low frequency (V.L.F.) radio waves propagating in an ionlzed medium, such as the ionosphere and exosphere, may exhibit markedly different characteristics from those of frequencies such as are used for communication in the short-wave bands. The anisotropy introduced into the medium by the presence of the earth's magnetic field has a significant effect, while at frequencies below about 5KHz the presence of heavy positive ions may further affect propagation. In particular it is found that, under suitable conditions, V.L.F. signals may propagate along paths closely following the lines of force of the earth's magnetic field. The study of such signals has a practical interest in that, from consideration of their propagation times and dispersion properties, they can provide an inexpensive method of determining electron densities at well beyond the range of satellite investigation. For this reason, if for no other, theoretical investigation of the paths traced in a model exosphere may indicate how closely the model exosphere approximates the true one. A powerful method of tracing out these paths is by the use of "ray-tracing", provided the properties of the medium vary slowly in space, a condition not always fulfilled in practice. It has been the subject of this thesis to carry out ray-tracing studies, in particular noting the effects of the positive ions in the exosphere; effects which have not received much notice before as they were thought to be unimportant. Intro., p. 1-2.
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Date Issued: 1969

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Some aspects of the ecology of the citrus red mite, Panonychus citri (McGregor), in the Eastern Cape Province

- Keetch, D P

Authors: Keetch, D P
Date: 1969
Subjects: Citrus -- Diseases and pests -- South Africa -- Eastern Cape Plant mites -- Ecology -- South Africa Citrus red mite Citrus red mite -- Ecology
Language: English
Type: Thesis , Doctoral , PhD
Identifier: vital:5860 , http://hdl.handle.net/10962/d1012630
Description: The citrus red mite, Panonychus citri (McGregor), is a relatively new pest to South African citriculture, the first recorded injury to citrus trees was from Rustenberg, Transvaal in 1950 (Smith 1953). In the U.S.A. the biology of this mite has been studied by Quayle (1938), Prendergast (1938), English and Turnipseed (1941), DeBach (1947), DeBach et al. (1950), Ebeling (1959) and Jeppson et al. (1957,1961). However, in South Africa little information is available concerning the ecolopy of the citrus red mite. The majority of the literature pertaining to P. citri in Republic, (Smith (1953), Mentz (1954), Stofberg (1959), Schwartz (1965) and Brodrick (1965) is of a descriptive nature, and mainly concerned with the chemical control of the mite. The only biological investigation on the development of P.citri, and the effect of insecticides and insect predators on its biology, under South African conditions, was made by van Rooyen (1966) at Zebediela, Transvaal. In the control of citrus pests, such as the citrus red mite, that need for a better understanding of their ecology has been well emphasised by DeBach (1951) and Griffiths (1951). DeBach (1951) in particular, stressed the danger of the continued reliance on insecticidal treatment as the only method of nest control, and has pointed out that persistent chemical applications may only serve to intensify the pest problem. He has suggested that a closer study of the environment of the pest species could provide a solution to the problems now encountered as a result of insecticidal control measures. Intro., p. 1-2.
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Date Issued: 1969

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